One in an occasional series on attempts to solve a medical mystery.

'I can't move my head" was the first thing our 2-year-old daughter, Sarah, said to me on a cold wintry morning several years ago, as she awakened from a deep sleep.

Instinctively, I felt her forehead. Her skin was on fire.

I was a second-year pediatric resident at the time. Our training prepared us to consider the worst first, and then to work backward to the probable.

"Meningitis, encephalitis, septic shock!" These potential diagnoses filled me with dread as I stared at our baby, her eyes pleading with me to make her better.

I quickly touched her neck where she said it hurt and felt a large swollen gland just below her jawline. "Cervical adenitis," also known as an infected lymph node, I thought to myself, mildly impressed with my diagnostic skills. A visit later that day to our pediatrician confirmed this diagnosis, and she was put on antibiotics to clear the infection.

Clear-cut? Not for a child of a pediatrician-in-training.

After two days of antibiotics, she still had high fevers and a persistent swollen lymph node.

Back to our pediatrician we went for what is called "failure of outpatient therapy." This is usually followed by the solemn utterance: "We will have to admit her to the hospital for intravenous antibiotics."

I knew this was what needed to be done, but having your child hospitalized is daunting enough for parents of sick kids. But having witnessed the errors that can occur in a hospital heightened my angst as my wife and I went home to pack an overnight bag.

A seminal 1999 report by the Institute of Medicine, "To Err Is Human," documented the tens of thousands of preventable deaths from medical errors that occur each year in U.S. hospitals.

Those findings began swimming in my head as I stared helplessly at Sarah, sleeping restlessly in her booster seat.

Unfortunately, the overnight bag we packed would not supply our family with enough clothes for the events about to unfold.

Two days into the hospitalization, Sarah still had high fevers and the swollen lymph node, but nothing else.

When I told the medical staff that we recently traveled to visit my in-laws in El Paso, Texas, this prompted lab tests for everything from the common (strep) to the unusual (Leptospira, a bacterium found in mammal urine). Nothing.

Some thought it might be scarlet fever or measles.

Rheumatic fever was a possibility. Even systemic juvenile arthritis was considered.

Was it one of those or something else?

On the fifth day of her illness, when Sarah woke up from a 15-hour slumber, I immediately noticed that her eyes were bloodshot. And a new symptom had emerged: a body rash.

The solution is on Page 7.